Hello,
I can confirm that this file fails with MKIV, but works fine with MKII. It seems that supp-mps is not loaded under MKIV.
does there exist a workaround for mkiv? I tried \usemodule[chemic] \input supp-mps \starttext \startchemical \chemical[SIX,B1..6,R1..6,RZ1..3][CH_3,CH_3,OH] \stopchemical \stoptext but then I get ! Undefined control sequence. \writecheckedMPgraphic #1->\ifgrTEXgraphic \global \MPTEXgraphictrue \else \... \startMPgraphic ...hic \writecheckedMPgraphic {#1} \stopwritingMPgraphic \getMPdrawing ...ic \MPdrawingdata \stopMPgraphic \loadcurrentMPgraphic {}\d... \@@endchemicalpicture ...raphictrue \getMPdrawing }\wd 2=\!!zeropoint \ht 2=... \stopchemical ...calpicture \@@endchemicalpicture \egroup \ifnum \chemicaldr... l.8 \stopchemical ? thank you for you answer, Philipp.